The study of the ten"rate bacteriophage has been exceedingly useful in generating information about universal regulatory mechanisms. Regulation of gene expression by a system of transcription termination - antitermination, first described in phage, has now been seen in eukaryotic cells, in particular the control of c-myc and HIV gene expression. The cellular factors, viral proteins, and specific sites required for antitermination are partially understood in the phage lambda system, and almost completely unknown for phage HKO22. The differences and similarities between these two phages, as well as the interactions betwen their regulatory systems, is being explored. The approach is both genetic and biochemical, and involves the isolation of mutants, the overproduction and purification of regulatory proteins, and the construction of mutant sites. Another phage regulatory system, repression, is subject to control by a host function, RpsB (S2). The control is at the level of mRNA translation; the mehanism of this regulation will be determined by analysis of mutants and establishment of an in vitro translation system.